(Future value) Sarah Wiggum would like to make a single lump-sum investment and have $1.6 million at the time of her retirement in 28 years. She has found a mutual fund that expects to earn 6 percent annually. How much must Sarah invest today? If Sarah earned an annual return of 18 percent, how much must she invest today? a. If Sarah can earn 6 percent annually for the next 28 years, how much will she have to invest today? \$ (Round to the nearest cent.) b. If Sarah can earn 18 percent annually for the next 28 years, how much will she have to invest today? (Round to the nearest cent.)